Conduits having variable flow resistances are used, for example, in degassing lines of a cooling system for an internal combustion engine of a motor vehicle. Such conduits conventionally have, for example, a valve and a comparatively complex control mechanism. This sometimes proves to be a disadvantage in practice both from the point of view of construction space and weight and in terms of the complexity of the cooling system, for example as regards the electrical connections and control strategy, also, not least, also in respect of the need for movable structural parts or components (inter alia, because of the accompanying wear).
U.S. Pat. No. 7,637,892 B2 discloses an implantable variable infusion pump system which has a flux or flow resistance, for example in the form of a filament fitted into a capillary or of an insertion piece, in which case the insertion piece will be composed of an electroactive polymer.